7 multiple pregnancies occurred in a series of 20 pregnancies after oocyte recovery for in-vitro fertilisation and embryo transfer. After ovarian stimulation with clomiphene alone or with human menopausal gonadotropin, 102 laparoscopies were carried out in 62 women and the ongoing pregnancy rate beyond the first trimester was 17/102 laparoscopies (17%), including 5 sets of twins. 1 triplet and 1 twin pregnancy showed evidence of regression of two sacs and one sac, and both are progressing as singleton pregnancies at 16 and 34 weeks, respectively. 3 abortions occurred at 7, 8, and 9 weeks--a spontaneous abortion rate of 15%. The pregnancy and multiple pregnancy rates after stimulation with clomiphene alone or with human menopausal gonadotropin were comparable, but oocyte pickup based on a knowledge of the duration of the endogenous rise in luteinising hormone, rather than 36 h after administration of human chorionic gonadotropin, increased the pregnancy rate. As the quality and number of embryos transferred to the uterus increased, the risk of multiple pregnancy also rose. Consideration should therefore be given to restricting the number of embryos transferred to limit multiple pregnancies to twins.